Conventionally, as an attachment structure of a clip for being attached to a wall body of a mounting member such as a protector, a transmission equipment, the interior of a vehicle or others, there is disclosed one in which the attachment is made by fitting elastic retaining pieces in a retaining hole in the wall body (for example, see PTL 1 to 3). FIGS. 6 to 9 are views showing a conventional attachment structure of a clip. FIG. 6 is a perspective view of the attachment structure. FIG. 7 is a plan view as seen from the top in FIG. 6, and A indicates a position where the clip is attached to the wall body of the mounting member. FIG. 8 is an enlarged view of the portion A of FIG. 7. FIG. 9 is a cross-sectional view taken along the line A1-A1 of FIG. 8. The attachment structure of the clip shown in FIGS. 6 to 9 comprises a retaining hole 11 formed in the wall body 10 of the mounting member, and the clip 1 having a retaining head 7 to be inserted in this retaining hole 11. This clip 1 includes a base portion 2 holding an article such as a wire harness or a base portion 2 attached to other equipment body, a clip pillar 3 formed upright on this base portion 2, the retaining head 7 comprising a pair of elastic retaining pieces 4, 4 depending from this clip pillar 3, and a pair of elastically-bendable press-contacting pieces 6 formed on and extending slantingly from the base portion 2.
For attaching the clip 1 of the above construction to the wall body 10 of the mounting member having the above construction, first, the retaining head 7 of the clip 1 is inserted into the retaining hole 11 in the wall body 10 from the outer side of the wall body 10 toward the inner side thereof. Then, the elastic retaining pieces 4 are pressed in a closing direction by an inner peripheral edge of the retaining hole 11 and are deformed, and when the retaining head 7 is further inserted deeper, step retaining portions 5 of the elastic retaining pieces 4 reach an upper end portion of the retaining hole 11, and the elastic retaining pieces 4 are elastically restored in an opening direction, so that the retaining step retaining portions 5 are retained on an open edge portion of the retaining hole 11.
In this manner, the clip 1 is attached to the wall body 10 of the mounting member, and in this condition, when some force F1, F2, F3 was applied to the clip 1 (see FIG. 9), there was a possibility that the portion around the retaining hole 11 was deformed depending on the thickness T and material of the wall body 10 of the mounting member, so that the retaining engagement of the step retaining portions 5 of the elastic retaining pieces 4 with the open edge portion of the retaining hole 11 might be canceled.
In addition, the strength of the wall body 10 of the mounting member was reduced as a result of formation of the retaining hole 11 therein, and therefore this led to the reduction of the strength of a mounting member body.
Furthermore, when some force F1 was applied to the elastic retaining piece 4 of the clip 1 by contact of an electric wire or others in the condition in which the clip was attached to the wall body 10 of the mounting member, there was a possibility that the elastic retaining piece 4 was deformed in the closing direction, so that the retaining engagement of the step retaining portions 5 of the elastic retaining pieces 4 with the open edge portion of the retaining hole 11 might be canceled.
And, in the case of the clip 1 having the press-contacting pieces 6 as shown in FIG. 9, the function of the press-contacting pieces 6, that is, the function of preventing the shaking of the clip 1, can not be efficiently performed if the relation between a length L2 from a retaining surface of the step retaining portion 5 of the elastic retaining piece 4 to a press-contact surface of the press-contacting piece 6 and the thickness T of the wall body 10 of the mounting member is not so determined as to establish L2≦T, that is, if a clearance L1 is not provided between the press-contact surface of the press-contacting piece 6 and the wall body 10 of the mounting member.
Therefore, in the case of using the clip 1 having the press-contacting pieces 6, the length L2 between the retaining surface of the step retaining portion 5 of the elastic retaining piece 4 and the press-contact surface of the press-contacting piece 6 must be selected according to the thickness T of the wall body 10 of the mounting member, and therefore the range of selection of the clip was narrow.